A resource treatment method for pickling water containing beryllium oxalate

Abstract

The invention discloses a resource treatment method for beryllium-containing oxalic acid water, including oil removal, conditioning and decomplexation, evaporation concentration, cooling crystallization and step-by-step precipitation treatment process. The process removes oils in oxalic acid water by pretreatment, then adds a decomplexing agent to weaken or release the complex state of oxalic acid with iron, aluminum and beryllium, improves the yield and purity of recovered oxalic acid, and then concentrates the oxalic acid water by evaporation to increase the oxalic acid concentration in the water, and finally recovers oxalic acid crystals by condensation crystallization centrifugation, and the evaporated condensate is reused to prepare oxalic acid water. After the mother liquor is respectively deoxidized by two-stage step-by-step precipitation, the supernatant is discharged into comprehensive wastewater. The method for recovering oxalic acid in oxalic acid water of the invention has the characteristics of simple process operation and low recovery cost, realizes the efficient recovery and resource utilization of oxalic acid in oxalic acid water containing metal ions such as iron and aluminum, and provides a new method for recovering oxalic acid in high-concentration oxalic acid water.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial wastewater treatment and environmental protection, and in particular relates to a method for treating wastewater containing beryllium. Background Art

[0002] The Degussa process is mostly used in the production of industrial beryllium oxide. After smelting, beryllium ore is used to prepare beryllium hydroxide through acid leaching-step impurity removal-precipitation. In the process of removing impurities such as iron and aluminum by step-by-step precipitation, part of the beryllium precipitates into the slag phase with the iron and aluminum, resulting in a low beryllium recovery rate. In order to improve the beryllium recovery rate, the industrial beryllium oxide production process is adjusted, and the extraction method is used to directly extract and recover the beryllium in the beryllium leachate. Since part of the iron and aluminum enter the organic phase after extraction with the beryllium, it is necessary to use oxalic acid solution to wash and purify the organic phase to remove impurities such as iron and aluminum, and then use it to prepare industrial beryllium hydroxide. This process can greatly improve the beryllium recovery rate, but the beryllium-containing oxalic acid washing water produced by washing the organic phase has the characteristics of high concentration, strong corrosiveness, and complex water quality, which is difficult to reuse directly. The conventional precipitation method has too high a processing cost and produces a large amount of waste residue, which seriously pollutes the environment. Since the oxalic acid washing water is derived from the washing wastewater containing impurities such as iron and aluminum produced by washing the organic phase after beryllium extraction with a high concentration oxalic acid solution during the industrial beryllium oxide production process, the oxalic acid content in the washing water is greater than 45g / L, and it contains a large amount of iron and aluminum. Since iron and aluminum coordinate with oxalate ions to form a stable complex, it is very difficult to remove the iron and aluminum impurities in the oxalic acid washing water.

[0003] In the prior art, lime neutralization is used to treat oxalic acid wastewater, which uses lime to neutralize the oxalic acid in the wastewater. After neutralization, the wastewater is discharged after simple treatment. 2- The reaction generates CaC2O4•2H2O with lower solubility. After solid-liquid separation, oxalic acid is recovered in the form of calcium oxalate and then converted into oxalic acid for reuse through activation. In this method, iron and oxalic acid are precipitated at the same time, and the oxalic acid precipitation rate is low, which affects the quality and recovery efficiency of activated oxalic acid, and the processing cost is very high. In addition, this method also has problems such as large lime consumption, large waste residue output, difficult and costly wastewater and waste residue disposal.

[0004] In the prior art, there is also an evaporation crystallization method for treating oxalic acid wastewater, which directly uses evaporation, crystallization, filtration and other processes to recover oxalic acid. If the evaporation crystallization method is used to directly perform evaporation, concentration and crystallization, the recovered oxalic acid has a high impurity content, a low recovery rate and a high treatment cost. This method also has the problems of high energy consumption, serious equipment corrosion and high treatment cost.

[0005] In order to significantly improve the economic benefits of industrial beryllium oxide production, efficient and cost-effective oxalic acid wash water resource treatment technology is urgently needed. Summary of the invention

[0006] In order to overcome the problems in the prior art, the present invention provides a resource treatment method for beryllium-containing oxalic acid pickling water. After the beryllium-containing oxalic acid pickling water is treated with a decomplexing agent, evaporation concentration-cooling crystallization is adopted to recover oxalic acid, thereby realizing the recovery of oxalic acid and improving the oxalic acid recovery rate and oxalic acid purity. After crystallization, the mother liquor is subjected to step-by-step precipitation to remove the remaining oxalic acid and recover beryllium. The recovered oxalic acid and beryllium meet the production requirements and are directly returned for use. On the basis of reducing the amount of hazardous waste residue generated and the amount of wastewater discharged, the comprehensive recovery and utilization of the valuable resources of the oxalic acid pickling water is realized.

[0007] In order to solve the above technical problems, the technical solutions proposed by the present invention are as follows:

[0008] The present invention provides a resource treatment method for beryllium-containing pickling water, comprising the following steps:

[0009] S1. Remove oil from beryllium oxalate pickling water by flotation treatment.

[0010] S2. Add a decomplexing agent to the beryllium oxalate pickling water from which the oil substances have been removed in step S1 to obtain solution A.

[0011] S3, evaporating and concentrating the solution A obtained in step S2, and then condensing it, and when it drops to the crystallization temperature, centrifuging and separating it to obtain oxalic acid crystals and mother solution B.

[0012] S4. Add a calcium-containing precipitant to the mother liquor B until the pH value is 3-6, perform the first solid-liquid separation to obtain a first-stage supernatant, and then add sodium hydroxide to the first-stage supernatant until the pH value is 8-9, perform the second solid-liquid separation to obtain a second-stage supernatant.

[0013] As an optional embodiment, in the preparation method provided by the present invention, the beryllium-oxalic acid washing water is washing wastewater containing iron and aluminum impurities generated by washing the organic phase after beryllium extraction with a high-concentration oxalic acid solution in the industrial beryllium oxide production process.

[0014] The beryllium-containing oxalic acid washing water in the present invention is the washing wastewater containing iron and aluminum impurities produced by washing and extracting the organic phase of beryllium with a high-concentration oxalic acid solution in the production process of industrial beryllium oxide. The oxalic acid content in the washing water is greater than 45g / L, and it contains a large amount of iron and aluminum. Since iron and aluminum coordinate with oxalate ions to form a stable complex, a decomplexing agent is added to form a more stable complex with iron and aluminum, and oxalic acid is converted into oxalic acid molecules and released, thereby improving the oxalic acid recovery rate and oxalic acid purity. At the same time, by controlling the dosage of the decomplexing agent, the temperature rise range of the material boiling point is controlled, and conventional evaporation and concentration technology is used. The condensate obtained after condensation treatment can be used to prepare oxalic acid washing water, and oxalic acid crystals are obtained after further cooling and crystallization, and oxalic acid washing water can be prepared. For the mother liquor after cooling and crystallization, the oxalic acid (sulfuric acid) and beryllium are removed step by step by controlling the pH value and adding a precipitant, and the generated beryllium-rich slag is returned to the beryllium ore smelting section. During the first precipitation, the pH value is controlled at 3-6, which is conducive to using calcium-containing precipitants to remove residual oxalic acid and excess decomplexing agents in the solution. During the second precipitation, the pH value is controlled at 8-9 after adding sodium hydroxide, which is conducive to the formation of beryllium hydroxide precipitation and the removal of beryllium ions in the solution. The oxalic acid and beryllium recovered in the entire process have certain economic benefits compared with the treatment costs. On the basis of reducing the amount of hazardous waste residues and wastewater discharge, the comprehensive recycling and utilization of valuable resources of oxalic acid washing water is realized.

[0015] As an optional embodiment, in the preparation method provided by the present invention, the beryllium oxalate pickling water contains a complex formed by oxalic acid and iron ions and a complex formed by oxalic acid and aluminum ions, and the oxalic acid content in the beryllium oxalate pickling water is 45-60 g / L, the iron ion concentration is 0.1-5 g / L, the aluminum ion concentration is 0.1-5 g / L, and the beryllium ion concentration is 0.05-0.5 g / L.

[0016] The present invention finds that the beryllium-oxalic acid pickling water contains complexes formed by oxalic acid and iron ions and complexes formed by oxalic acid and aluminum ions, which are relatively stable. If directly subjected to evaporation, concentration and crystallization treatment, the recovered oxalic acid has a high impurity content, a low recovery rate and a high treatment cost. Therefore, the present invention first adds a decomplexing agent, forms a more stable complex with iron and aluminum by adding the decomplexing agent, and converts oxalic acid into oxalic acid molecules to be freed, thereby improving the oxalic acid recovery rate and oxalic acid purity.

[0017] As an optional embodiment, in the preparation method provided by the present invention, the decomplexing agent is selected from one or more of citric acid, sulfosalicylic acid, sulfuric acid, and ethylenediaminetetraacetic acid.

[0018] The function of the decomplexer in the present invention is to release the complex formed by the coordination of iron and aluminum with oxalate ions, utilize the decomplexer to form a more stable complex with iron and aluminum, and make oxalic acid become oxalic acid molecules and be freed, so as to facilitate the recovery of oxalic acid in the next step.

[0019] Furthermore, the decomplexing agent is a mixture of sulfuric acid and sulfosalicylic acid, and the mass ratio of sulfuric acid to sulfosalicylic acid in the mixture is 1:1.

[0020] As an optional embodiment, in the preparation method provided by the present invention, the amount of the decomplexing agent added is 1-3% of the mass of the beryllium oxalate pickling water, and the action time after adding the decomplexing agent is 5-20 minutes.

[0021] In the present invention, adding a decomplexing agent containing 1-3% of the mass of beryllium oxalate pickling water is beneficial to improving the oxalic acid recovery rate and oxalic acid purity, while controlling the temperature rise range of the material boiling point. If it exceeds the above range, it will affect the evaporation temperature and the quality of the recovered oxalic acid crystals.

[0022] As an optional embodiment, in the preparation method provided by the present invention, in step S3, the evaporation concentration temperature is 105° C. to 120° C., and the evaporation concentration ratio is 4 to 7.

[0023] In the present invention, the evaporation concentration temperature is determined to be 105° C. to 120° C. by analyzing the solution composition, and the temperature rises with the increase of concentration. At the same time, a suitable evaporation device is selected according to the temperature during the evaporation process.

[0024] As an optional embodiment, in the preparation method provided by the present invention, in step S3, oxalic acid crystals containing crystal water are obtained after centrifugal separation, and the oxalic acid product is obtained after drying.

[0025] In the present invention, the oxalic acid molecules are freed by adding a decomplexing agent, and oxalic acid crystals are obtained by evaporation, concentration and crystallization, thereby realizing the recovery of most of the oxalic acid in the beryllium-containing oxalic acid pickling water.

[0026] As an optional embodiment, in the preparation method provided by the present invention, the purity of the oxalic acid product is ≥96%, and the recovery rate is >85%.

[0027] As an optional embodiment, in the preparation method provided by the present invention, in step S3, the crystallization temperature is 10-20°C.

[0028] In the present invention, the crystallization temperature is 10-20° C. In this temperature range, the solubility and crystal purity of oxalic acid are both excellent, and the cost is relatively suitable, without the need to add additional cooling equipment.

[0029] As an optional embodiment, in the preparation method provided by the present invention, in step S4, precipitate A is obtained after the first solid-liquid separation, and precipitate A is calcium oxalate slag (containing gypsum slag). After the second solid-liquid separation, precipitate B is obtained, and precipitate B is beryllium hydroxide precipitate, which is returned to the beryllium ore smelting section.

[0030] After adding lime milk in the present invention, the remaining oxalic acid in the solution and the added decomplexing agent sulfuric acid form precipitation and are removed, and after adding sodium hydroxide, the beryllium in the solution forms beryllium hydroxide precipitation and is removed, and the obtained beryllium-rich slag is returned to the beryllium ore smelting section.

[0031] As an optional embodiment, in the preparation method provided by the present invention, in step S4, the calcium-containing precipitant is lime milk or calcium carbonate.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The resource treatment method of beryllium-oxalic acid pickling water provided by the present invention not only reduces the generation of acidic wastewater and beryllium-containing hazardous waste residues, avoids environmental pollution, but also recovers oxalic acid and beryllium, thereby achieving better economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 This is a flow chart for resource recovery of pickling water containing beryllium oxalate. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0038] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0039] Example 1

[0040] like Figure 1 As shown, the beryllium-containing oxalic acid washing water in this embodiment is the washing wastewater containing iron and aluminum impurities produced by washing the organic phase after beryllium extraction with a high-concentration oxalic acid solution in the industrial beryllium oxide production process, wherein C 草酸 =45.0g / L, C Be =0.1g / L, CFe =2.0g / L, C Al =1.8g / L, 3m 3 , the processing steps are as follows:

[0041] Pump the beryllium oxalate pickling water into the flotation treatment tank, turn on the flotation machine to remove oil. Add 60kg of decomplexing agent (sulfuric acid: citric acid mass ratio = 1:1) and stir for 10 minutes. Use triple-effect evaporation to evaporate and concentrate 5 times at normal pressure and 108℃-114℃. Cool the concentrated liquid to 20℃ and cool it for crystallization. Centrifuge to separate the oxalic acid crystals, recover the oxalic acid, and return the condensate to the front end for the preparation of oxalic acid pickling water.

[0042] The crystallization mother liquor is precipitated by lime milk and step-by-step neutralization. First, lime milk is added until the pH value of the mother liquor is 5 for precipitation. After solid-liquid separation, calcium oxalate slag (including gypsum slag) is obtained. Sodium hydroxide is added to the supernatant until the pH value of the solution is 8 for precipitation. After solid-liquid separation, beryllium-rich slag is obtained, and the supernatant is discharged to the comprehensive wastewater.

[0043] A total of 210.6 kg of oxalic acid dihydrate crystals were recovered (the oxalic acid purity was 96.7% after low-temperature drying), with an oxalic acid recovery rate of 86.2%. The impurity contents of iron, aluminum, etc. in the recovered oxalic acid met the impurity content indicators in "GB / T 1626-2008 Industrial Oxalic Acid", and 142.5 kg of calcium oxalate slag (including gypsum slag) (calculated as dry slag) and 7.8 kg of beryllium-rich slag (containing 3.1% beryllium, returned to the beryllium ore roasting section) were produced.

[0044] Example 2

[0045] The beryllium-containing oxalic acid washing water in this embodiment is the washing wastewater containing iron and aluminum impurities produced by washing the organic phase after beryllium extraction with a high-concentration oxalic acid solution in the industrial beryllium oxide production process. 草酸 =55.0g / L, C Be =0.2g / L, C Fe =1.98g / L, C Al =1.77g / L, 3m 3 , the processing steps are as follows:

[0046] Pump the beryllium oxalate pickling water into the flotation treatment tank, turn on the flotation machine to remove oil. Add 90kg of decomplexing agent (sulfuric acid: sulfosalicylic acid mass ratio = 1:1) and stir for 10 minutes. Use triple-effect evaporation to evaporate and concentrate 6 times at normal pressure and 108℃-120℃. Cool the concentrated liquid to 15℃ and cool it for crystallization. Centrifuge to separate the oxalic acid crystals, recover the oxalic acid, and return the condensate to the front end for the preparation of oxalic acid pickling water.

[0047] The crystallization mother liquor is treated with lime milk and step-by-step neutralization precipitation. First, lime milk is added to the mother liquor until the pH value is 6 for precipitation. After solid-liquid separation, calcium oxalate slag (including gypsum slag) is obtained. Sodium hydroxide is added to the supernatant until the pH value of the solution is 9. After solid-liquid separation, beryllium-rich slag is obtained, and the supernatant is discharged to the comprehensive wastewater.

[0048] After testing, a total of 271.0 kg of oxalic acid dihydrate crystals were recovered (the oxalic acid purity was 96.2% after low-temperature drying), the oxalic acid recovery rate was 90.3%, and the impurity contents of iron, aluminum and other impurities in the recovered oxalic acid met the impurity content indicators in "GB / T 1626-2008 Industrial Oxalic Acid". 152.2 kg of calcium oxalate slag (including gypsum slag) was produced (calculated as dry slag) and 8.1 kg of beryllium-rich slag (containing 5.9% beryllium, returned to the beryllium ore roasting section) were produced.

[0049] Example 3

[0050] The beryllium-containing oxalic acid washing water in this embodiment is the washing wastewater containing iron and aluminum impurities produced by washing the organic phase after beryllium extraction with a high-concentration oxalic acid solution in the industrial beryllium oxide production process. 草酸 =55.0g / L, C Be =0.2g / L, C Fe =1.98g / L, C Al =1.77g / L, 3m 3 , the processing steps are as follows:

[0051] Pump the beryllium oxalate pickling water into the flotation treatment tank, turn on the flotation machine to remove oil. Add 30kg of decomplexing agent (sulfuric acid: citric acid mass ratio = 1:1) and stir for 10 minutes. Use triple-effect evaporation to evaporate and concentrate 4 times at normal pressure and 108℃-120℃. Cool the concentrated liquid to 10℃ and cool it to crystallize. Centrifuge to separate oxalic acid crystals, recover oxalic acid, and return the condensate to the front end for water preparation of oxalic acid pickling water.

[0052] The crystallization mother liquor is treated with lime milk and step-by-step neutralization precipitation. Lime milk is first added to the mother liquor until the pH value is 4 for precipitation. After solid-liquid separation, calcium oxalate slag (including gypsum slag) is obtained. Sodium hydroxide is added to the supernatant until the pH value of the solution is 8. After solid-liquid separation, beryllium-rich slag is obtained, and the supernatant is discharged to the comprehensive wastewater.

[0053] After testing, a total of 271.0 kg of oxalic acid dihydrate crystals were recovered (the oxalic acid purity was 96.1% after low-temperature drying), the oxalic acid recovery rate was 85.3%, and the impurity contents of iron, aluminum, etc. in the recovered oxalic acid met the impurity content indicators in "GB / T 1626-2008 Industrial Oxalic Acid". 133.94 kg of calcium oxalate slag (including gypsum slag) was produced (calculated as dry slag), and 7.3 kg of beryllium-rich slag (containing 3.3% beryllium, returned to the beryllium ore roasting section) was produced.

[0054] Comparative Example 1

[0055] The beryllium oxalate pickling water used in Example 1 in this comparative example contains 3 m 3 , the processing steps are as follows:

[0056] Pump the beryllium oxalate pickling water into the flotation treatment tank, turn on the flotation machine to remove the oil. Evaporate and concentrate 5 times at normal pressure and 108℃-114℃, cool the concentrate to 20℃ and cool it for crystallization, centrifuge to separate the oxalic acid crystals, recycle the oxalic acid, and return the condensate to the front end for the preparation of oxalic acid pickling water.

[0057] The crystallization mother liquor is treated with lime milk and step-by-step neutralization precipitation. First, lime milk is added to the mother liquor until the pH value is 6 for precipitation. After solid-liquid separation, calcium oxalate slag (including gypsum slag) is obtained. Sodium hydroxide is added to the supernatant until the pH value of the solution is 9. After solid-liquid separation, beryllium-rich slag is obtained, and the supernatant is discharged to the comprehensive wastewater.

[0058] After testing, a total of 149.8 kg of oxalic acid dihydrate crystals were recovered (the oxalic acid purity was 95.1% after low-temperature drying), the oxalic acid recovery rate was 60.3%, and the impurity content of iron, aluminum and other impurities in the recovered oxalic acid exceeded the impurity content indicators in "GB / T 1626-2008 Industrial Oxalic Acid". 410.9 kg of calcium oxalate slag (including gypsum slag) was produced (calculated as dry slag), and 7.5 kg of beryllium-rich slag was produced (containing 3.2% beryllium, which was returned to the beryllium ore roasting section).

[0059] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for recycling beryllium-containing pickling water, characterized in that: The following steps are involved: S1. Removing oily substances from beryllium-containing pickling water by flotation treatment; S2, adding a decomplexing agent to the beryllium-oxalic acid washing water from which the oil substances have been removed in step S1, so that the oxalic acid is converted into free oxalic acid molecules, thereby obtaining a solution A; S3, evaporating and concentrating the solution A obtained in step S2, and then condensing it, and when it drops to the crystallization temperature, centrifuging and separating it to obtain oxalic acid crystals and mother solution B; S4. Add a calcium-containing precipitant to the mother liquor B until the pH value is 3-6, perform the first solid-liquid separation to obtain a first-stage supernatant, and then add sodium hydroxide to the first-stage supernatant until the pH value is 8-9, perform the second solid-liquid separation to obtain a second-stage supernatant.

2. The resource treatment method of beryllium oxalate-containing pickling water according to claim 1, characterized in that: The beryllium-oxalic acid washing water is washing wastewater containing iron and aluminum impurities generated by washing the organic phase after beryllium extraction with a high-concentration oxalic acid solution in the industrial beryllium oxide production process.

3. The resource treatment method of beryllium oxalate-containing pickling water according to claim 1, characterized in that: The beryllium oxalate pickling water contains a complex formed by oxalic acid and iron ions and a complex formed by oxalic acid and aluminum ions. The oxalic acid content in the beryllium oxalate pickling water is 45-60 g / L, the iron ion concentration is 0.1-5 g / L, the aluminum ion concentration is 0.1-5 g / L, and the beryllium ion concentration is 0.05-0.5 g / L.

4. The resource treatment method of beryllium-containing oxalate pickling water according to claim 1, characterized in that: In step S2, the decomplexing agent is selected from one or more of citric acid, sulfosalicylic acid, sulfuric acid, and ethylenediaminetetraacetic acid.

5. The resource treatment method of beryllium-containing oxalate pickling water according to claim 4, characterized in that: The decomplexing agent is a mixture of sulfuric acid and sulfosalicylic acid, and the mass ratio of sulfuric acid to sulfosalicylic acid in the mixture is 1:

1.

6. The resource treatment method for beryllium oxalate-containing pickling water according to any one of claims 1 to 5, characterized in that: In step S2, the amount of the decomplexing agent added is 1-3% of the mass of the beryllium oxalate pickling water, and the action time after adding the decomplexing agent is 5-20 minutes.

7. The resource treatment method of beryllium-containing oxalate pickling water according to claim 1, characterized in that: In step S3, the evaporation concentration temperature is 105°C-120°C, the evaporation concentration ratio is 4-7, and the crystallization temperature is 10-20°C; after the centrifugal separation, oxalic acid crystals containing crystal water are obtained, and the oxalic acid product is obtained after drying.

8. The resource treatment method of beryllium oxalate-containing pickling water according to claim 7, characterized in that: The purity of the oxalic acid product is ≥96%, and the recovery rate is >85%.

9. The resource treatment method of beryllium-containing oxalate pickling water according to claim 1, characterized in that: In step S4, after the first solid-liquid separation, precipitate A is obtained, and the precipitate A is calcium oxalate slag. After the second solid-liquid separation, precipitate B is obtained, and the precipitate B is beryllium hydroxide. The precipitate B is returned to the beryllium ore smelting section.

10. The resource treatment method of beryllium-containing oxalate pickling water according to claim 1, characterized in that: In step S4, the calcium-containing precipitant is lime milk or calcium carbonate.

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